Repair or remanufacture of blade platform for a gas turbine engine

ABSTRACT

A method of remanufacturing a turbine blade having a platform includes placing a puck against a surface of the platform. The method may include electrical discharge machining an interface between the puck and the platform and brazing the puck to the platform. A total radial thickness of a finally remanufactured platform of the remanufactured turbine blade is greater than an initial radial thickness of the platform before remanufacturing the turbine blade.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/482,273, filed on Sep. 10, 2014. The disclosure of the aboveapplication is incorporated herein by reference.

FIELD

The present disclosure relates to a gas turbine engine and, moreparticularly, to a repair or remanufacture procedure for a componentthereof.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

Gas turbine engines generally include a gas generator with a compressorsection to pressurize an airflow, a combustor section to burn ahydrocarbon fuel in the presence of the pressurized air, and a turbinesection to extract energy from the resultant combustion gases. In anindustrial gas turbine (IGT) engine, a core gas stream generated in thegas generator is passed through a power turbine section to producemechanical work.

The core gas stream downstream of combustor section may subject theturbine components to pressure gradients, temperature gradients, andvibrations that may result in thermal-mechanical fatigue cracks.Eventually, the turbine components may need to be replaced multipletimes over the engine service life. Replacement of such components isrelatively expensive such that there are often considerable economicincentives to repair these components.

SUMMARY

A method of remanufacturing a turbine component according to onedisclosed non-limiting form of the present disclosure includeselectrical discharge machining a puck via the turbine component to forman electrical discharged machined puck; and brazing the electricaldischarged machined puck to the turbine component.

A further form of the present disclosure includes electrical dischargemachining the puck via an underplatform of the turbine component.

A further form of any of the foregoing forms of the present disclosureincludes, wherein the turbine component is a turbine blade.

A further form of any of the foregoing forms of the present disclosureincludes, wherein electrical discharge machining the puck via theturbine component results in an interface gap between the electricaldischarged machined puck and the turbine component of less than about0.005″ (0.127 mm).

A further form of any of the foregoing forms of the present disclosureincludes manufacturing the puck from a braze presintered preform (PSP)prior to the electrical discharge machining.

A further form of any of the foregoing forms of the present disclosureincludes casting the puck prior to the electrical discharge machining.

A further form of any of the foregoing forms of the present disclosureincludes machining the puck prior to the electrical discharge machining.

A further form of any of the foregoing forms of the present disclosureincludes tack welding the electrical discharged machined puck to theturbine component prior to the brazing.

A method of remanufacturing a platform of a turbine blade, according toanother disclosed non-limiting form of the present disclosure electricaldischarge machining a puck via an underplatform of the platform to forman electrical discharged machined puck; and brazing the electricaldischarged machined puck to the underplatform to increase the thicknessof the platform.

A further form of any of the foregoing forms of the present disclosureincludes, wherein electrical discharge machining the puck results in aninterface gap between the electrical discharged machined puck and theunderplatform of less than about 0.005″ (0.127 mm).

A further form of any of the foregoing forms of the present disclosureincludes manufacturing the puck from a braze presintered preform (PSP)prior to the electrical discharge machining.

A further form of any of the foregoing forms of the present disclosureincludes tack welding the electrical discharged machined puck to theturbine component prior to the brazing.

A turbine blade with a platform for a gas turbine engine according toanother disclosed non-limiting form of the present disclosure includesan underplatform of the platform; and an electrical discharged machinedpuck brazed to the underplatform, an interface gap between theelectrical discharged machined puck and the underplatform less thanabout 0.005″ (0.127 mm).

A further form of any of the foregoing forms of the present disclosureincludes, wherein the interface gap is about 0.0005″-0.0045″(0.0127-0.1143 mm).

A further form of any of the foregoing forms of the present disclosureincludes, wherein the electrical discharged machined puck issemi-circular.

A further form of any of the foregoing forms of the present disclosureincludes, wherein the underplatform is a suction side of the platform.

A further form of any of the foregoing forms of the present disclosureincludes, wherein the electrical discharged machined puck includes amultiple of features.

A further form of any of the foregoing forms of the present disclosureincludes, wherein the electrical discharged machined puck includes amultiple of chevron-shaped turbulators opposite the underplatform.

A further form of any of the foregoing forms of the present disclosureincludes, wherein the electrical discharged machined puck includes amultiple of ribs opposite the underplatform.

A further form of any of the foregoing forms of the present disclosureincludes, wherein the electrical discharged machined puck has athickness of about 0.030″-0.375″ (0.762-9.525 mm).

The foregoing features and elements may be combined in variouscombinations without exclusivity, unless expressly indicated otherwise.These features and elements as well as the operation of the inventionwill become more apparent in light of the following description and theaccompanying drawings. It should be understood, however, the followingdescription and drawings are intended to be exemplary in nature andnon-limiting.

Further areas of applicability will become apparent from the descriptionprovided herein. It should be understood that the description andspecific examples are intended for purposes of illustration only and arenot intended to limit the scope of the present disclosure.

DRAWINGS

Various features will become apparent to those skilled in the art fromthe following detailed description of the disclosed non-limiting form.In order that the disclosure may be well understood, there will now bedescribed various forms thereof, given by way of example, referencebeing made to the accompanying drawings, in which:

FIG. 1 is a schematic cross-section of one example gas turbine engine;

FIG. 2 is a schematic view of an example gas turbine engine in anindustrial gas turbine environment;

FIG. 3 is an enlarged schematic cross-section of a turbine section ofthe engine;

FIG. 4 is an enlarged perspective view of a turbine rotor and singlerepresentative rotor blade of the engine;

FIG. 5 is an expanded view of an underplatform region of the rotorblade;

FIG. 6 is a flowchart illustrating a method to repair/remanufacture aplatform of a turbine blade according to one disclosed non-limitingform;

FIG. 7 is a perspective view of an example puck that is EDM to increasethe thickness of the turbine blade platform;

FIG. 8 is a perspective view of an underplatform region of the turbineblade with a puck according to one disclosed non-limiting form;

FIG. 9 is a perspective view of an underplatform region of the turbineblade with a puck according to another disclosed non-limiting form;

FIG. 10 is a perspective view of an underplatform region of the turbineblade with a puck according to another disclosed non-limiting form; and

FIG. 11 is a perspective view of an underplatform region of the turbineblade with a puck according to another disclosed non-limiting form.

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses. Itshould be understood that throughout the drawings, correspondingreference numerals indicate like or corresponding parts and features.

FIG. 1 schematically illustrates a gas turbine engine 20. The gasturbine engine 20 generally includes a compressor section 24, acombustor section 26, a turbine section 28, a power turbine section 30,and an exhaust section 32. The engine 20 may be installed within aground-mounted enclosure 40 (FIG. 2) typical of an industrial gasturbine (IGT). Although depicted as specific engine architecture in thedisclosed non-limiting form, it should be understood that the conceptsdescribed herein are not limited to only such architecture as theteachings may be applied to other gas turbine architectures.

The compressor section 24, the combustor section 26, and the turbinesection 28 are collectively referred to as a gas generator that isoperable to drive the power turbine section 30. The power turbinesection 30 drives an output shaft 34 to power a generator 36 or othersystem. In one disclosed non-limiting form, the power turbine section 30includes a free turbine with no physical connection between the gasgenerator and the power turbine section 30. The generated power is athereby a result of mass flow capture by the otherwise free powerturbine.

With reference to FIG. 3, an enlarged schematic view of a portion of theturbine section 28 is shown by way of example; however, other enginesections will also benefit herefrom. A full ring shroud assembly 60mounted to an engine case structure 36 supports a Blade Outer Air Seal(BOAS) assembly 62 with a multiple of circumferentially distributed BOAS64 proximate to a rotor assembly 66 (one schematically shown). The fullring shroud assembly 60 and the BOAS assembly 62 are axially disposedbetween a forward stationary vane ring 68 and an aft stationary vanering 70. Each vane ring 68, 70 includes an array of vanes 72, 74 thatextend between a respective inner vane platform 76, 78, and an outervane platform 80, 82. The outer vane platforms 80, 82 are attached tothe engine case structure 36.

The rotor assembly 66 includes an array of blades 84 (one shown in FIG.4) circumferentially disposed around a disk 86. Each blade 84 includes aroot 88, a platform 90, and an airfoil 92. Each blade root 88 isreceived within a rim 94 of the disk 86 such that the airfoils 92 extendradially outward so that a tip 96 of each airfoil 92 is adjacent theBOAS assembly 62. The blades 84 are typically manufactured of, forexample, a Nickel Alloy.

Combustion gases produced in the combustor section 26 (indicatedschematically by arrow C) expand in the turbine section 28 and producepressure gradients, temperature gradients, and vibrations. The turbinecomponents in the turbine section 28 are thereby subject tothermal-mechanical fatigue that, over time, may generate cracks in thesecomponents.

With reference to FIG. 5, the platform 90 generally separates the root88 and the airfoil 92 to define an inner boundary of the core gas path.The airfoil 92 defines a blade chord between a leading edge 98, whichmay include various forward and/or aft sweep configurations, and atrailing edge 100. A first airfoil sidewall 102 that may be convex todefine a suction side, and a second airfoil sidewall 104 that may beconcave to define a pressure side are joined at the leading edge 98 andat the axially spaced trailing edge 100. The platform 90 includes a gaspath side 106 adjacent to the airfoil 92 and a non-gas path side 108adjacent to the root 88. Here, the non-gas path side 108 of the platform90 generally below the second airfoil sidewall 104 is referred to as theunderplatform 110.

Thermal-mechanical fatigue cracks may occur on the underplatform 110 andcan be removed via machining. This machining, however, thins theplatform 90, and applicant has determined that the frequency andamplitude of occurrence of such cracks resulting from use subsequent tosuch machining is related to the thickness of the platform 90. Thethickness of the platform 90, in an exemplary form may range from about0.100-0.200 inches (2.5-5.1 mm), depending in part upon casting and/orprevious repairs.

With reference to FIG. 6, one disclosed non-limiting form of a repairmethod 200 initially includes manufacture of a puck 120 (FIG. 7; step202). The puck 120 may be machined, cast, or otherwise manufacturedfrom, for example, a superalloy with grains that will be aligned withthe engine axis A. Alternatively, the puck 120 may be manufactured frombraze presintered preform (PSP). Such initial manufacture provides apuck 120 with dimensions that are close to the underplatform pocketformed by blade 84.

The puck 120, in this disclosed non-limiting form, is generallysemi-circular in shape with an arcuate side 122 that closely fitsadjacent to the blade root 88 and a straight side 124 that generallyaligns with an edge 90A (FIG. 5) of the platform 90. The puck 120includes end sections 126, 128 that may be clipped or otherwise shapedfor engagement within the underplatform 110 pocket of the non-gas pathside 108 (FIG. 7). In this disclosed non-limiting form, the puck 120 ishas a thickness of about 0.030″-0.375″ (0.762-9.525 mm).

Next, the puck 120 is subject to Electrical discharge machining (EDM)(step 204). Electrical discharge machining (EDM) is a highly accuratemethod of machining metal materials in which material is removed fromthe workpiece by a series of rapidly recurring current dischargesbetween two electrodes separated by a dielectric liquid, and subject toan electric voltage. One electrode is referred to as the tool-electrode,or simply, the ‘tool,’ while the other is referred to as theworkpiece-electrode, or ‘workpiece.’ Generally, the ‘tool’ serves as aworking electrode to facilitate removal of material from the‘workpiece’. Here, the polarity is reversed from normal EDM operationsuch that the blade 84 is the working electrode and the puck 120 is themachined part. That is, the underplatform 110 of the blade 84 (the‘tool’), electro discharge machines the puck 120 (the ‘workpiece’).

The puck 120 is plunged into the underplatform 110 to remove materialfrom the puck 120 until both parts create a near perfect fit one toanother. Such a near perfect fit enhances braze strength, as it isdesired for braze faying surfaces to have a gap no larger than about0.005″ (0.127 mm). That is, the puck 120 is initially cast and/ormachined to be close to the dimension of the area of the underplatform110, then subjected to the reverse EDM process to obtain a close-fittinggap therebetween. Trials have shown a finished gap of about0.0005″-0.0045″ (0.0127-0.1143 mm).

Next, the puck 120 and the underplatform 110 area are weld prepared(step 206). Weld preparation includes, but is not limited to, forexample, degreasing, fluoride-ion cleaning, grit blast, hydrogen furnaceclean, vacuum clean and/or others.

Next, the EDM machined platform puck 120 is then located in the bladeunderplatform 110 pocket and tack welded thereto (step 208). It shouldbe appreciated that various methods may be alternatively or additionallyprovided to affix the puck 120 to the underplatform 110 so as tofacilitate brazing (step 210).

A braze slurry is then applied around a perimeter of the puck 120 andsubsequently brazed via the application of heat to the blade 84, puck120, and braze slurry (step 210). The braze slurry flows over and aroundthe puck 120 to join the puck 120 to the underplatform 110. Sincebrazing does not melt the base metal of the joint, brazing allows muchtighter control over tolerances and produces a clean joint withminimal-if-any need for secondary finishing. Additionally, dissimilarmetals and non-metals (i.e. metalized ceramics) can be brazed. That is,the puck 120 may be manufactured of a material dissimilar to that of theblade 84.

The braze slurry is readily received into the close finished gapinterface between the platform puck 120 and the underplatform 110 viacapillary action to provide an effective braze therebetween. That is,the reverse EDM interface provides a close-fitting interface thatfacilitates a high strength brazed interface and does not further reducethe thickness of the platform 90.

Finally, the finished braze B may be blended and coated to form adesired profile (step 212; FIG. 8). The blend may be performed by handand/or by machine operations.

With reference to FIG. 9, the platform puck 120 can replicate the OEMshape of the underplatform, or incorporate improved cooling and/orstrengthening features such as chevron-shaped turbulators 300, amultiple of ribs 400 (FIG. 10), a multiple of dimples 500 (FIG. 11) orother such features. The features facilitate turbulation of a coolingairflow to further control the thermal effects on the turbine blade 84.

The method 200 provides a repair to a small portion of the component toincrease platform thickness with the remainder being identical to an OEMcomponent. The Reverse EDM machining also facilitates a relatively rapidrepair.

The use of the terms “a,” “an,” “the,” and similar are to be construedto cover both the singular and the plural, unless otherwise indicatedherein or specifically contradicted by context. The modifier “about”used in connection with a quantity is inclusive of the stated value andhas the meaning dictated by the context (e.g., it includes the degree oferror associated with measurement of the particular quantity). Allranges disclosed herein are inclusive of the endpoints, and theendpoints are independently combinable with each other. It should beappreciated that relative positional terms such as “forward,” “aft,”“upper,” “lower,” “above,” “below,” and the like are with reference tothe normal operational attitude of the vehicle and should not beconsidered otherwise limiting.

Although the different non-limiting forms have specific illustratedcomponents, the forms of this invention are not limited to thoseparticular combinations. It is possible to use some of the components orfeatures from any of the non-limiting forms in combination with featuresor components from any of the other non-limiting forms.

It should be appreciated that like reference numerals identifycorresponding or similar elements throughout the several drawings. Itshould also be appreciated that although a particular componentarrangement is disclosed in the illustrated form, other arrangementswill benefit herefrom.

Unless otherwise expressly indicated herein, all numerical valuesindicating mechanical/thermal properties, compositional percentages,dimensions and/or tolerances, or other characteristics are to beunderstood as modified by the word “about” or “approximately” indescribing the scope of the present disclosure. This modification isdesired for various reasons including industrial practice, manufacturingtechnology, and testing capability.

The description of the disclosure is merely exemplary in nature and,thus, variations that do not depart from the substance of the disclosureare intended to be within the scope of the disclosure. Such variationsare not to be regarded as a departure from the spirit and scope of thedisclosure.

As used herein, the phrase at least one of A, B, and C should beconstrued to mean a logical (A OR B OR C), using a non-exclusive logicalOR, and should not be construed to mean “at least one of A, at least oneof B, and at least one of C.”

What is claimed is:
 1. A method of remanufacturing a turbine bladehaving a platform, the method comprising: placing a puck against asurface of the platform; electrical discharge machining an interfacebetween the puck and the platform; and brazing the puck to the platform,wherein a total radial thickness of a finally remanufactured platform ofthe remanufactured turbine blade is greater than an initial radialthickness of the platform before remanufacturing the turbine blade. 2.The method according to claim 1, wherein the surface of the platform isa radially inward facing surface on an underplatform of the platform. 3.The method according to claim 2, wherein an entirety of the puck isdisposed radially inward of a gas path side of the platform.
 4. Themethod according to claim 1, wherein a gap between the puck and theplatform is less than 0.005″ (0.127 mm) after electrical dischargemachining.
 5. The method according to claim 1, further comprisinginstalling the finally remanufactured turbine blade into a turbineengine.
 6. The method according to claim 1, further comprisingmanufacturing the puck from a braze presintered preform (PSP).
 7. Themethod according to claim 1, further comprising manufacturing the puckby casting the puck.
 8. The method according to claim 1, furthercomprising tack welding the puck to the platform prior to brazing thepuck to the platform.
 9. The method according to claim 1, furthercomprising machining an underside of the platform to remove a crack fromthe platform and form the surface of the platform.
 10. The methodaccording to claim 9, wherein the underside of the platform is machinedto remove the crack without penetrating through a gas path surface ofthe platform.
 11. The method according to claim 1, further comprisingcoating the brazed puck.
 12. The method according to claim 1, wherein afull perimeter of the puck is surrounded by the platform.
 13. The methodaccording to claim 1, wherein a radially inward side of the puckincludes at least one of a turbulator, a rib, or dimples.
 14. The methodaccording to claim 1, wherein the electrical discharge machining isconfigured to remove material from the platform.
 15. A method ofremanufacturing a platform of a turbine blade, comprising: machining asurface of the platform to form a machined surface area of the platform,the platform having a machined radial thickness that is less than aninitial radial thickness of the platform; forming a puck so that thepuck has a shape that matches the machined surface area and forms aninterference gap with the machined surface area that is no larger than0.005″ (0.127 mm); locating the puck against the machined surface area;and attaching the puck to the platform, wherein the machined radialthickness and a puck radial thickness together are greater than theinitial radial thickness of the platform when remanufacturing of theplatform is complete.
 16. The method according to claim 15, whereinforming the puck includes one of: electrical discharge machining thepuck via the platform, co-electrical discharge machining the puck andthe platform, and electrical discharge machining the platform via thepuck.
 17. The method according to claim 15, wherein attaching the puckto the platform includes brazing the puck to the platform.
 18. Themethod according to claim 17, wherein a full perimeter of the puck issurrounded by the platform.
 19. The method according to claim 15,wherein the surface of the platform is a radially inward facing surfaceon an underplatform of the platform and the puck is disposed entirelyradially inward of a gas path side of the platform.
 20. A method ofremanufacturing a platform of a turbine blade, comprising: removingmaterial from a radially inward facing surface of the platform to removea crack from the platform and form a recess in the platform, a fullperimeter of the recess being surrounded by the platform; placing a puckagainst the recess; electrical discharge machining the puck so that thepuck has a shape that matches the recess with an interference gap thatis no larger than 0.005″ (0.127 mm); brazing the puck within the recess,wherein a total radial thickness of a finally remanufactured platform ofthe remanufactured turbine blade is greater than an initial radialthickness of the platform before remanufacturing the turbine blade.